It's annoying when it happends but if it's P2 just break them out asap. If it's P3 roll some raid cd's, have a hybrid help out if it's looking real dire. Doable but yeah, I don't like when it happends.

Yesterday Amber Shapper HC 2 try in a row :
1° construct : the healing monk, the disc said : " i have my CD i'm fine".
2° construct : the healing monk, the disc ask for some help from the SP.
3° construst : the healing monk, the raid said : "FUCK YOU RNG !"

Try 3 healing it, and make sure you're watching for the Parasite. Whoever has that debuff needs to be untouched when it comes to heals. If you have a Disc Priest then have them worry about Parasite targets because Shields will not increase the damage the target takes from the Parasite. In regards to constructs, as long as people are interrupting their personal Amber Explosions and the Monstrosity when it comes out then you shouldn't have much raid damage going out. You can easily spot heal for that phase. If something bad DOES happen then pop a CD and get everyone back up to full. (and watch your Parasite target for the extra damage)

During the last phase we tend to just rotate CDs and anyone who gets the Parasite either uses a personal CD to remove it (Cloak of Shadows) or we just try to hit them with as many absorbtion effects as we can. After that it's really not a healing fight, it's all about nuking down the boss with the constant constructs abilities and not blowing up the raid.